字符設備驅動模塊 之 基本通用模塊

字符設備驅動模塊 之 基本通用模塊

1. #include <linux/module.h>
2. #include <linux/types.h>
3. #include <linux/fs.h>
4. #include <linux/errno.h>
5. #include <linux/mm.h>
6. #include <linux/sched.h>
7. #include <linux/init.h>
8. #include <linux/cdev.h>
9. #include <asm/io.h>
10. #include <asm/system.h>
11. #include <asm/uaccess.h>
12. #include <linux/device.h> /* device_create()*/
14. #define ADC_SIZE 0x1000 /*全局內存最大4K字節*/
15. #define MEM_CLEAR 0x1 /*清0全局內存*/
16. #define ADC_MAJOR 250 /*預設的adc的主設備號*/
18. static int adc_major = ADC_MAJOR;
19. /*adc設備結構體*/
20. struct adc_dev {
23. struct cdev cdev; /*cdev結構體*/
24. unsigned char mem[ADC_SIZE]; /*全局內存*/
25. };
27. struct adc_dev *adc_devp; /*設備結構體指針*/
28. /*文件打開函數*/
29. int adc_open(struct inode *inode, struct file *filp)
30. {
31. /*將設備結構體指針賦值給文件私有數據指針*/
32. filp->private_data = adc_devp;
33. return 0;
34. }
35. /*文件釋放函數*/
36. int adc_release(struct inode *inode, struct file *filp)
37. {
38. return 0;
39. }
41. /* ioctl設備控制函數 */
42. static int adc_ioctl(struct inode *inodep, struct file *filp, unsigned
43. int cmd, unsigned long arg)
44. {
45. struct adc_dev *dev = filp->private_data;/*獲得設備結構體指針*/
47. switch (cmd) {
48. case MEM_CLEAR:
49. memset(dev->mem, 0, ADC_SIZE);
50. printk(KERN_INFO "adc is set to zero\n");
51. break;
53. default:
54. return - EINVAL;
55. }
57. return 0;
58. }
60. /*讀函數*/
61. static ssize_t adc_read(struct file *filp, char __user *buf, size_t size,
62. loff_t *ppos)
63. {
64. unsigned long p = *ppos;
65. unsigned int count = size;
66. int ret = 0;
67. struct adc_dev *dev = filp->private_data; /*獲得設備結構體指針*/
69. /*分析和獲取有效的寫長度*/
70. if (p >= ADC_SIZE)
71. return 0;
72. if (count > ADC_SIZE - p)
73. count = ADC_SIZE - p;
75. /*內核空間->用戶空間*/
76. if (copy_to_user(buf, (void *)(dev->mem + p), count)) {
77. ret = - EFAULT;
78. } else {
79. *ppos += count;
80. ret = count;
82. printk(KERN_INFO "read %u bytes(s) from %lu\n", count, p);
83. }
85. return ret;
86. }
88. /*寫函數*/
89. static ssize_t adc_write(struct file *filp, const char __user *buf,
90. size_t size, loff_t *ppos)
91. {
92. unsigned long p = *ppos;
93. unsigned int count = size;
94. int ret = 0;
95. struct adc_dev *dev = filp->private_data; /*獲得設備結構體指針*/
97. /*分析和獲取有效的寫長度*/
98. if (p >= ADC_SIZE)
99. return 0;
100. if (count > ADC_SIZE - p)
101. count = ADC_SIZE - p;
103. /*用戶空間->內核空間*/
104. if (copy_from_user(dev->mem + p, buf, count))
105. ret = - EFAULT;
106. else {
107. *ppos += count;
108. ret = count;
110. printk(KERN_INFO "written %u bytes(s) from %lu\n", count, p);
111. }
113. return ret;
114. }
116. /* seek文件定位函數 */
117. static loff_t adc_llseek(struct file *filp, loff_t offset, int orig)
118. {
119. loff_t ret = 0;
120. switch (orig) {
121. case 0: /*相對文件開始位置偏移*/
122. if (offset < 0) {
123. ret = - EINVAL;
124. break;
125. }
126. if ((unsigned int)offset > ADC_SIZE) {
127. ret = - EINVAL;
128. break;
129. }
130. filp->f_pos = (unsigned int)offset;
131. ret = filp->f_pos;
132. break;
133. case 1: /*相對文件當前位置偏移*/
134. if ((filp->f_pos + offset) > ADC_SIZE) {
135. ret = - EINVAL;
136. break;
137. }
138. if ((filp->f_pos + offset) < 0) {
139. ret = - EINVAL;
140. break;
141. }
142. filp->f_pos += offset;
143. ret = filp->f_pos;
144. break;
145. default:
146. ret = - EINVAL;
147. break;
148. }
149. return ret;
150. }
152. /*文件操作結構體*/
153. static const struct file_operations adc_fops = {
154. .owner = THIS_MODULE,
155. .llseek = adc_llseek,
156. .read = adc_read,
157. .write = adc_write,
158. .ioctl = adc_ioctl,
159. .open = adc_open,
160. .release = adc_release,
161. };
163. /*初始化並注冊cdev*/
164. static void adc_setup_cdev(struct adc_dev *dev, int index)
165. {
166. int err, devno = MKDEV(adc_major, index);
168. cdev_init(&dev->cdev, &adc_fops);
169. dev->cdev.owner = THIS_MODULE;
170. err = cdev_add(&dev->cdev, devno, 1);
171. if (err)
172. printk(KERN_NOTICE "Error %d adding LED%d", err, index);
173. }
175. struct class *myclass;
178. /*設備驅動模塊加載函數*/
179. int adc_init(void)
180. {
181. int result;
182. dev_t devno = MKDEV(adc_major, 0);
184. /* 申請設備號*/
185. if (adc_major)
186. result = register_chrdev_region(devno, 1, "adc");
187. else { /* 動態申請設備號 */
188. result = alloc_chrdev_region(&devno, 0, 1, "adc");
189. adc_major = MAJOR(devno);
190. }
191. if (result < 0)
192. return result;
194. /* 動態申請設備結構體的內存*/
195. adc_devp = kmalloc(sizeof(struct adc_dev), GFP_KERNEL);
196. if (!adc_devp) { /*申請失敗*/
197. result = - ENOMEM;
198. goto fail_malloc;
199. }
201. memset(adc_devp, 0, sizeof(struct adc_dev));
203. adc_setup_cdev(adc_devp, 0);
205. /*自動創建設備文件*/
206. myclass = class_create(THIS_MODULE,"test_char"); /*在sys下創建類目錄/sys/class/test_char*/
207. device_create(myclass, NULL, MKDEV(adc_major,0), NULL, "adc");
209. return 0;
211. fail_malloc:
212. unregister_chrdev_region(devno, 1);
213. return result;
214. }
216. /*模塊卸載函數*/
217. void adc_exit(void)
218. {
219. cdev_del(&adc_devp->cdev); /*注銷cdev*/
220. kfree(adc_devp); /*釋放設備結構體內存*/
221. unregister_chrdev_region(MKDEV(adc_major, 0), 1); /*釋放設備號*/
222. class_destroy(myclass);
223. device_destroy(myclass,MKDEV(adc_major,0));
224. }
226. MODULE_AUTHOR("Barry Song <21cnbao@gmail.com>");
227. MODULE_LICENSE("Dual BSD/GPL");
229. module_param(adc_major, int, S_IRUGO);
231. module_init(adc_init);
232. module_exit(adc_exit);
238. 用戶程序：
240. #include <stdio.h>
241. #include <stdlib.h>
242. #include <fcntl.h>
243. #include <unistd.h>
244. #include <string.h>
245. int main()
246. {
247. int fd;
248. char buf[4096];
250. strcpy(buf,"Mem is char dev!");
251. printf("Buf: %s\n",buf);
253. fd=open("/dev/adc",O_RDWR);
254. if(fd<0)
255. {
256. printf("open failed!\n");
257. return -1;
258. }
259. else
260. printf("open /dev/adc is success!\n");
261. if(write(fd,buf,sizeof(buf))<0)
262. {
263. printf("write failed!\n");
264. return -1;
265. }
266. else
267. printf("write: %s\n",buf);
268. lseek(fd,0,SEEK_SET);
270. strcpy(buf,"Buf is NULL!\n");
271. printf("Buf: %s\n",buf);
273. read(fd,buf,sizeof(buf));
275. printf("Buf: %s\n",buf);
277. return 0;